cartoonOne of the most frequently used rhetorical devices to avoid answering the questions of the critics of the AGW scare is the proposition that there is a astonishing scientific ‘consensus’ on the point: some 97 per cent of climate scientists are said to agree. By implication, the other 3 per cent are simply ignorant, mavericks or troublemakers, to be lumped in with other people who fall into the category ‘climate deniers’. We are thus asked to accept the authority of the consensus, and to cease and desist from questioning anything about global warming or ‘climate change’.

To deal with this part of the debate we need to go back to the beginning. The AGW scare is built around three core propositions: that the earth is warming, that the warming is caused by human activities, especially the burning of fossil fuels, and that the warming is dangerous. It is said, or implied, that 97 per cent of ‘climate scientists’ agree with this triad. In fact President Obama’s office tweeted exactly this statement in 2015: Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous.

Science is rarely a matter of consensus, and where it is so what we are usually talking about is the material that goes into textbooks, for beginning students need to have some understanding of what is generally agreed to be the case (some of what I learned in high school science is now generally agreed to be wrong or irrelevant). As students get to be more senior, they are exposed to argument, and taught to explore and test the hypotheses and evidence that lie behind what has been published. In experimental science, consensus is simply current opinion, and it can be quite wrong.

As Einstein said, when a group of scientists in 1931 published a book Hundert Autoren gegen Einstein (‘One hundred authors against Einstein’), ‘Why one hundred? If I were wrong, then one would be enough!’ That one would have conducted the experiment whose results showed conclusively that Einstein’s hypothesis must be wrong, but none of the hundred had done that. They were simply expressing their separate opinions.

Now, what do ‘climate scientists’ actually say? I’ve put inverted commas around the term because there is no agreed meaning for it. Most of the leading figures in this sub-field have degrees in other disciplines, whatever the title of their current chair. The ’97 per cent’ figure is supported by three different published articles, with a forerunner by Naomi Oreskes, about whom I wrote a little while ago. In 2004 she looked at 928 abstracts of articles in the climate science field. According to her, 75 per cent supported the view that human activities were responsible for most of the warming in the last fifty years.